To this day, fat bikers still argue about front suspension. While one crowd argues that it’s unnecessary, others (like myself) prefer the additional control suspension provides – when riding outside the normal groomed trails. It’s safe to say that the need for suspension is very condition dependent, but if you feel like it’s a benefit, the Manitou Mastodon has looked promising from the start.

Fat bike suspension fork review for Manitou Mastodon Pro EXT

Phil Ott gets sendy in North Carolina on an early Mastodon

We got our first look at the fork when I was down in North Carolina with the Hayes/Manitou crew to do a feature on their testing and development. It was immediately clear after watching Hayes Mobile Marketing Specialist Phil Ott shred the Bailey Mountain Bike Park on a full suspension fat bike equipped with a prototype Mastodon that this was not just a fat bike fork. No, the Mastodon was designed to be a mountain bike suspension fork that just happens to clear the biggest tires imaginable.

It was that last part that made things difficult.

Fat bike suspension fork review for Manitou Mastodon Pro EXT Fat bike suspension fork review for Manitou Mastodon Pro EXT

Stiffness is a virtue

One of the most common complaints with the Rock Shox Bluto is that it’s not stiff enough for larger or more aggressive riders. To be honest, that’s sort of to be expected when you widen a fork with a 32mm chassis to fit larger tires, though I’ve never had major qualms with the Bluto. However, I’m also 5’8″ and 160lbs with all my gear, so I rarely have issues with things being too noodly.

However, the Mastodon is about more than just making a stiffer fork. Manitou wanted to ensure that the Mastodon would clear every size fat bike tire that currently exists, in addition to making a stiffer fork (and making it E-MTB certified). That meant using a 34mm chassis which is the same as many of their MTB suspension forks, but with a massively reinforced Reverse Arch. Admittedly, at certain angles, the arch isn’t the most attractive design, but it’s certainly functional.

Fat bike suspension fork review for Manitou Mastodon Pro EXT Fat bike suspension fork review for Manitou Mastodon Pro EXT

Between the arch, the forged aluminum hollow crown, and the Hexlock SL 15 x 150mm axle, the increased stiffness is immediately noticeable. It’s worth noting that our test fork came without any grease under the threaded Hexlock SL cap on the non-drive side. After a trip to the beach, the axle had already started to seize in place, so it’s highly recommended to pull the threaded cap (which holds the captured 6mm allen bolt in place) and grease between the two surfaces in addition to the threaded portions of the axle and other contact points.

Fat bike suspension fork review for Manitou Mastodon Pro EXT Fat bike suspension fork review for Manitou Mastodon Pro EXT

EXTended Tire Clearance

While all of the Mastodon fork arches will technically clear every tire, the actual tire clearance of the fork depends on the model. On test here is the Mastodon Pro EXT – which is an important distinction. Just because a fork arch clears a tire, doesn’t mean the fork is compatible. The important measurement is whether the tire clears the crown of the fork on full compression.

That’s where the EXT comes in. In order to offer clearance for tires up to 796mm in diameter, the EXT forks are limited in their travel so that the tire can’t contact the crown. That also means that a 100mm EXT suspension fork has the axle to crown measurement of a 120mm standard fork – this is a critical detail when ordering the right fork for your bike. 

The fork shown above is pictured with one of the tallest fat bike tires we know of at the moment – the 27.5 x 4.5″ Terrene Cake Eater which measures about 791mm tall on ENVE rims. The fork also clears 26 x 5.0″ tires, with a maximum tire width of 131mm (which is the same for the STD or EXT model). If you’re confused about tire clearance, Manitou has broken it down into a handy chart here. Generally though, the STD forks will clear up to a 4″ tire, while the EXT is needed for anything larger than 4″.

Fat bike suspension fork review for Manitou Mastodon Pro EXT

Alafia River State Park in Florida is an absolute blast – even on a fat bike.

That tire clearance of the EXT model opens up the possibility to build some true monster fat bikes with the versatility of riding through incredibly soft sand one day, and shredding mountain bike trails the next. Granted the massive tires were probably more a hindrance than benefit on the trails of Alafia River State Park, but I still had massive amounts of fun – and certainly made the most out of having a suspension fork on the front of the bike.

This is where you have to make your own call when it comes to suspension forks on a fat bike. Are you primarily going to be riding packed snow in the winter? Or will you find yourself riding mountain bike trails in all conditions, along with the occasional jump, drop, or staircase? If you’re in that latter category, suspension can be a very welcomed addition to a fat bike regardless of tire size.

Fat bike suspension fork review for Manitou Mastodon Pro EXT Fat bike suspension fork review for Manitou Mastodon Pro EXT

Suspension Performance

Trail riding also brought out the best of the Mastodon in terms of the suspension performance. Like the 34mm chassis, the Mastodon borrows much of the air spring and damping technology from Manitou’s other forks including their Dorado Air Spring with IVA (Incremental Volume Adjust) and MC² compression damping with TPC rebound damping. The IVA allows you to adjust the air spring volume and progressiveness without any additional spacers (you just reposition the spacers already on the IVA shaft), which allows the Mastodon to be extremely supple off the top, yet ramp up for big hits. Adjustable high and low speed compression damping allows you to tune for brake dive and helps to firm up the suspension when you don’t need it. The adjustable cartridge TPC rebound damping rounds out the adjustments for excellent tuning control.

Fat bike suspension fork review for Manitou Mastodon Pro EXT

Realistically, if you’re riding wheels and tires this big, you should be running big rotors which is why the Mastodon starts with a 180mm post mount front brake.

As for the travel numbers, the Pro Mastodon is available in 100mm (which is internally adjustable down to 80mm) and 120mm (which is internally adjustable up to 140mm). There is also a 150mm travel version, but it is only available OEM.

Fat bike suspension fork review for Manitou Mastodon Pro EXT

Final Thoughts

Overall, the Mastodon has performed exactly as claimed. It is indeed a much stiffer fat bike suspension fork that rides just as well as any other single crown fork from Manitou – which is to say it is impressively supple and offers excellent control through the suspension travel. It’s clear that Manitou has done their homework when it comes to fat bikes, which isn’t surprising considering that they’re based in Wisconsin.

So who is the Mastodon for? At 2239g, my 100mm travel Mastodon Pro EXT comes in right at claimed (2210g for the 100mm STD version). But that still makes it substantially heavier than something like a Rock Shox Bluto (1,840g), and way heavier than the Lauf Carbonara (1,120g). That means the Mastodon is probably not for the weight weenies. However, if you’re a rider on the heavier end of the spectrum, or you ride your fat bike like any other mountain bike (hard), the added stiffness and suspension performance will be welcomed. Finally, if you’re looking for the most tire clearance for the biggest tires (plus mud, snow, ice, etc.), it’s hard to beat the Mastodon EXT in terms of sheer size.

The Mastodon Pro STD/EXT is priced at $849.99, while the slightly heavier Comp version with lower end damping is available for $649.99.


  1. Brad J Sedola on

    The difference between this fork and the Bluto is night and day. It’s far more supple than the Bluto. The final straw was maintenance on the Bluto. Having to tear it apart every 3 rides to keep it running smooth was where I drew the line. The Mastodon is still running like butter 4 months later.

    • Mike Rosinski on

      Brad – seems to me your fork was a factory defect, did you submit warranty claim?
      Seriously hope you did, absolutely no fork should need tear down every 3 rides.
      Please let me know as I’m a new owner of a 2020 Framed Alaskan Carbon with the Bluto, and curious your resolution.

  2. craigmedred on

    My Wren is plusher than a Bluto, too; stiffer than a baseball bat; and it’s still running like butter after a year of use. But it doesn’t have 140mm of travel. Then again, who needs 140mm of travel on a fatty?

    • Cody Frank on

      Hells yeah I have a Wren too. Stiff as they get. Adjustable and light. I have 110 mm of travel and only bottomed out on the first few rides. Raced it and saved my ass more than once. God bless the Wren..

  3. David on

    Hi! Just to understand what’s in the article… If my fat bike has a rigid fork and it is 100 mm suspension corrected, should I get the 100 mm or the 80 mm EXT fork, knowing the 100 mm is like a 120 mm STD? Thanks!

    • Zach Overholt on

      If you want to run up to 26×5.15” / 27.5×4.5” tires, you’ll need the EXT version. The standard version will fit up to 26×4” / 27.5×3.8” tires. So if you are planning on running the larger tires and your frame is suspension corrected to 100mm, the best fit will be an 80mm EXT fork. I don’t believe the EXT fork is sold in 80mm, but the 100mm travel EXT fork is internally adjustable down to 80mm. Hope that helps.


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